The broad field of metal working is replete with ways to join two pieces of metal together including joining a metal tube with a non-tubular piece. For example, U.S. Pat. Nos. 4,584,765 (Gray), 4,782,571 (Krips et al.) and 5,004,047 (Meier et al.) all involve joining metal parts to one another to make a heat exchanger.
The joint described in the Krips et al. patent, which involves a relatively-thin-wall tube expanded outwardly against a thick slab, is stated to be "pressure-tight." Welding is used to join the tube and slab.
U.S. Pat. No. 4,212,099 (Williams et al.) describes a method of making a tube-and-plate connection in which an aperture having plural slots is formed in the plate. The metal is then formed into a shallow cup shape having what may be termed a zigzag edge and the fingers are bent back toward the plate. The tube is nested into the fingers and the fingers and tube are crimped together.
U.S. Pat. No. 4,334,703 (Arthur et al.) shows a tube-and-plate connection involving a flange with a tube around the flange. For joining, the side wall of the tube and the flange are both radially, outwardly pierced at one or more places around their circumferences. A stated reason for piercing is to prevent relative rotation of the tube and the flange. Other than at the locations of pierced holes, neither the tube end nor the flange are deformed from their cylindrical shapes. And, of course, piercing destroys any possibility of gas sealing between the tube and flange.
While these prior art approaches to joining a tube and plate have been generally satisfactory for their intended purposes, they are not well suited to join a tube and plate having approximately equal wall thicknesses and requiring a gas-tight seal. Nor are certain of such approaches suitable where protrusion of any structure from but one side of the plate is desired.
The connection described in the Arthur et al. patent pierces the tube and plate at the joint and the method of the Williams et al. patent has protrusions from both side of the plate. It seems doubtful that the Williams et al. method yields a gas-tight seal. Apparently it need not--tubes and plates so joined are used inside a vehicle exhaust muffler surrounded by an outer shell. And the tooling required in the Williams et al. and Arthur et al. methods seems a bit complex.
An improved method for joining a tube and a plate which may be used with tubes and plates having approximately equal wall thicknesses, which results in a protrusion from only one side of the plate, which requires no welding, which is gas-tight and which uses relatively-simple tooling would be an important advance in the art.